No need to cut a slit on 60-66, I installed plates using an old antenna & some duct tape. You will need to remove filler neck on driver's side. I welded a nut to a plate made out of 1/8" sheet steel. Stuck the plate up inside the pillar using antenna/duct tape combo. I then plug-welded the plate thru some extra holes I drilled around the mounting hole, but later I realized I could have used epoxy to mount it, it only has to keep from turning while you are bolting seat belt down. Brian
